Two-column option and subcommand blocks in the manual were falling through
to the indented-code fallback, rendering as an unhighlighted grey slab on
the site. `_as_table` detects a contiguous, column-aligned indented run and
emits a headerless GFM table instead; anything it cannot prove is tabular
still takes the old path.
15 blocks convert, 20 are correctly left alone. The concat and man-page
outputs are untouched — `prettify` is site-only, and the byte-exact
round-trip test stays green.
rootiest
67fb29687c